Examine the scenario illustrated in the figure. The straight wire...

The magnetic field due to the straight wire carrying current $i_1$ is directed into the plane of the paper at the location of the loop.

The magnetic forces on the top and bottom horizontal segments of the loop are equal in magnitude and opposite in direction, cancelling each other out.

The left vertical segment carries current in the same direction as the straight wire. Parallel currents attract, so it experiences an attractive force $F_1$ towards the wire.

The right vertical segment carries current in the opposite direction to the straight wire. Antiparallel currents repel, so it experiences a repulsive force $F_2$ away from the wire.

The magnitude of the magnetic field produced by the straight wire decreases with distance ($B = \dfrac{\mu_0 i_1}{2\pi r}$).

Since the left segment is closer to the straight wire than the right segment, the magnetic field is stronger at the left segment. Therefore, the attractive force $F_1$ is greater than the repulsive force $F_2$.

The net force on the loop is directed towards the straight wire, causing the loop to move towards it.